from django.http import HttpResponseRedirect
from django.shortcuts import get_object_or_404, render
from django.urls import reverse
from django.views import generic
from .models import Choice, Question
from django.utils import timezone

class IndexView(generic.ListView):

    template_name = 'polls/index.html'
    context_object_name = 'latest_question_list'
    def get_queryset(self):
        """
        返回最后五个已发布的问题（不包括将来要发布的问题）。
        """
        return Question.objects.filter(
            pub_date__lte=timezone.now()
        ).order_by('-pub_date')[:5]

class DetailView(generic.DetailView):
    model = Question
    template_name = 'polls/detail.html'
    def get_queryset(self):
        """
        排除任何尚未发布的问题。
        """
        return Question.objects.filter(pub_date__lte=timezone.now())

class ResultsView(generic.DetailView):
    model = Question
    template_name = 'polls/results.html'

def vote(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    try:
        selected_choice = question.choice_set.get(pk=request.POST['choice'])
    except (KeyError, Choice.DoesNotExist):
        # Redisplay the question voting form.
        return render(request, 'polls/detail.html', {
            'question': question,
            'error_message': "您没有选择。",
        })
    else:
        selected_choice.votes += 1
        selected_choice.save()
        # Always return an HttpResponseRedirect after successfully dealing
        # with POST data. This prevents data from being posted twice if a
        # user hits the Back button.
        return HttpResponseRedirect(reverse('polls:results', args=(question.id,)))